The correct answer is:
You would use the associative property to regroup the numbers so that you have easily recognizable products to multiply together.
We can regroup these factors as 10 × (4 × 2). This gives us the product in parentheses, 4×2 = 8. Next multiply this by 10; 8×10 = 80. Regrouping like this helps us to solve the problem more quickly.